In gas turbine engines, especially those used in aerospace applications, it is desirable to optimise the use of any available space, particularly where efficiency, volume reduction and weight reduction are primary considerations. In many cases, such as in an air-intake of an aircraft, the space available for a heat exchanger is curved.
Previously, a curved heat exchanger has been achieved by providing a plurality of cuboid-shaped heat exchanger cores connected together with wedge portions located between each core. The wedge portions provide manifolds to direct fluid from one core to the next and to ensure that adjacent cores are angled with respect to one another, thus providing the heat-exchanger with an overall curved shape. However, these wedge portions do not contribute to the heat exchanger performance.
Another curved heat exchanger has been achieved using a continuously curved core of a plate design. While the design avoids the need for wedge portions, the nature of a plate heat exchanger can present limitations on the performance. To try to maximise heat transfer, formations are required within the flow paths but these are restricted to serrated or turbulator type fins. These realistically limit the unit type to being an air-liquid or liquid-liquid due to the poor air performance for this type of fin. Further, because of the curved shape, the serrated or turbulator fins have to be oriented normal to the overall flow direction which can compromise performance. The curved plate heat exchangers must also be fabricated using a salt bath braze joining process.
Laminated heat exchangers are also known, and an example is described in EP-A-2474803. These comprise a plurality of planar (i.e. non-curved) laminate members that are stacked on top of one another to define a plurality of internal channels. The channels are formed by hollows provided in pairs of laminate members. Sets of such laminate members, each defining either part of a first flow path for a first fluid stream or a second flow path for a second fluid stream, are stacked alternately to produce the heat exchanger. A three dimensional laminated structure is thus built up from the laminated members, and within this structure there are arranged the plurality of channels for the first and second fluid streams. The resulting stack of laminate members defining the interleaved flow paths, is then brazed together to form a laminated heat exchanger.